The present invention relates to Computer Numerical Control (CNC) machines and more particularly to a method and system for converting graphic based computer programs from various sources into numeric control (NC) code in order to control the operation of a CNC based machine.
In a typical CNC machine installation, workpiece processing programs are generated at a location separate from the machine, generally in an office environment. This type of programming is commonly referred to as xe2x80x9coff-linexe2x80x9d programming. While it is possible to generate programs at the machine, doing so can be economically prohibitive. Two factors contribute to such result. First, the CNC machine is an integrated production tool. In order to serve in a programming capacity, the CNC machine must be removed from production. Second, generating programs at the machine control requires the operator either to enter each axis movement as a line of NC code or to generate cut paths with a hand-held pendant as the machine executes each axis movement. Because they often consume a considerable number of hours per program, neither of these methods is more efficient than off-line methods.
A typical off-line process begins with the generation of a workpiece program using computer aided manufacturing (CAM) software. The program is then post-processed. Post-processing typically includes selection of tooling, assignment of various feed rates, nesting of cutting profiles into patterns that provide for maximum material utilization, and configuring the program into a specific machine format suitable for use by a CNC machine control. After the program has been completely processed off-line, it may be loaded into the control of a CNC machine center from magnetic storage media or sent directly to the machine through a local area network or a direct NC (DNC) link.
While off-line programming provides several significant advantages over the older, more conventional method of generating programs at the machine, it has certain shortcomings. For instance, the process is rather inflexible. Parameters such as tool selection and feed speeds, generated off-line, cannot be modified at the CNC control without great difficulty. When a program is conventionally post-processed, it is configured for a specific machine format and cannot be used on any other machine without going through the complete post-processing procedure again. It would be decidedly advantageous to have the ability to post process a program, to input and modify program parameters, and to configure the program automatically for the proper machine format at the machine control. This would allow a wide variety of off-line generated programs to be used on a diverse group of machines more efficiently.
Accordingly, the principal object of the present invention is to provide an improved method of converting a diverse group of off-line-generated computer programs into numeric control code in order to control a CNC machine system.
Another object of the invention is to provide method of programming a CNC machine control in such a way as to combine the benefits of off-line programming with the flexible selection of operational attributes at the machine control.
A further object of the invention is to provide a method of nesting at the machine control, workpieces and individual components of workpieces into clusters in order to maximize the use of available material.
A still further object of the invention is to provide a method of recording, tracking and matching off-fall sheets to nested clusters in order to optimize the use of available material.
A more specific object of the invention is to provide a system for carrying out at the central of a CNC machines the conversion of off-line generated computer programs into numeric control code in order to control such system, including means for nesting workpieces and components of workpieces into clusters and means for recording, tracking and matching off-fall sheet to nested clusters.
The present invention addresses the above-described problem by disclosing a method of converting off-line-generated component geometry programs into NC code in the CNC machine control. A program is presented to the machine control, where it is automatically configured for machine-specific attributes such as axis configuration and worktable size and layout. Control over various operational attributes such as tool selection and feed rates are assigned to the machine operator. The invention also provides for the utilization of off-fall (material left over from previous cutting operations) by recording and tracking off-fall as it is generated, automatically selecting suitably sized off-fall sheets, then nesting multiple workpieces or components of workpieces thereon for maximum material utilization. The use of off-fall, which frequently consists of sizable sheets of material, presents an economically beneficial and environmentally conscious alternative to wasting the material through disposal.